A two-stroke engine having transfer channels is disclosed in German patent publication 2,624,249. An ancillary outlet opening is provided in this two-stroke engine to reduce the development of noise during idle. The outlet is connected to the combustion chamber via this ancillary outlet opening during the downward stroke of the piston already in advance of the opening of the main outlet.
With an ancillary outlet opening of this kind, the running performance of the two-stroke engine can be improved when starting and during idle. However, the exhaust-gas values at full load of the two-stroke engine are thereby deteriorated.